Six hours of on-track action split into two sessions found reigning series champion Simon Pagenaud atop the time sheet at the end of the day. The driver of the No. 1 DXC Technology Team Penske Chevrolet clocked the best lap late in the four-hour afternoon session, at 1 minute, 16.6511 seconds (112.014 mph) on the 12-turn, 2.385-mile permanent road course.

Pagenaud sits fourth in the standings heading into Sunday's 85-lap race, 34 points behind his Team Penske teammate Newgarden. With double the normal race points available, Pagenaud is one of seven drivers with a mathematical shot as the Verizon IndyCar Series championship will be decided in the last race for a 12th consecutive year.

"We had a great day today," said Pagenaud, who won the 2016 Sonoma race from the pole position to clinch the championship. "We wanted to explore a direction. We have a new Firestone tire this year, so we have to forget a little bit about what we did last year and be curious and try things.

"It was a very interesting session. The car feels really good, I feel really good. Everyone feels really excited in the group. It's fun so far."

Pagenaud led three Team Penske drivers atop the time sheet. Helio Castroneves was second at 1:16.7530 (111.865 mph) in the No. 3 Hitachi Chevrolet and Will Power third (1:17.0550, 111.427 mph) in the No. 12 Verizon Chevrolet. Castroneves is third in the standings, 22 points behind Newgarden. Power is fifth in points, 68 out of the lead.

Newgarden, meanwhile, was ninth on the day with a lap of 1:17.3491 (111.003 mph) in the No. 2 hum by Verizon Team Penske Chevrolet. Chip Ganassi Racing's Scott Dixon, just three points behind Newgarden, was sixth fastest with a lap of 1:17.3016 (111.071 mph) in the No. 9 NTT Data Honda.

Sebastien Bourdais, winner of the 2017 season opener at St. Petersburg, was the fastest non-Penske driver in the open test. The Dale Coyne Racing driver took the No. 18 UNIFIN Honda for a lap of 1:17.2175 (111.192 mph).

"I feel like we have a pretty decent car with us," said Rossi, winner of the most recent Verizon IndyCar Series race two weeks ago at Watkins Glen International. "We're missing a little right now, but we're in the window, so it's all right.

"We knew that our baseline car was pretty decent, so we tried some things today. They weren't the right direction, so we came back to a baseline car at the end of the day. It was P5."

The day's lone incident occurred when reigning Indianapolis 500 winner Takuma Sato went off course in Turn 6, sustaining significant rear-end damage to the No. 26 Andretti Autosport Honda that ended his day about an hour before conclusion of the session. Sato was unhurt.

The GoPro Grand Prix of Sonoma race weekend officially starts with two practices on Friday, at 10 a.m. and 2:15 p.m. local time. NBCSN airs the second practice live beginning at 2 p.m.

Verizon P1 Award qualifying to determine the pole sitter airs live at 3:30 p.m. Saturday on NBCSN and the Advance Auto Parts INDYCAR Radio Network. The race to decide the 2017 championship airs live at 3:30 p.m. Sunday on NBCSN and the Advance Auto Parts INDYCAR Radio Network.

Tickets are still available for the GoPro Grand Prix of Sonoma, Sept. 15-17, including the Total Access Package, which includes a reserved-seat ticket and a garage/pit/pre-race pass for $99. Kids 12 and under are admitted FREE and parking is FREE all weekend. For more information, visit sonomaraceway.com/indycar or call 800-870-7223.

Featured Event

The Toyota/Save Mart 350 roars into Sonoma June 22-24, and it’s guaranteed to be a wild ride. It’s the biggest rush to hit wine country, and you won’t want to miss a second of the action on and off track. Be sure to get your tickets as NASCAR tackles its first road course of the season.